CERES :: Browsing by Author "Balleri, Alessio"

Browsing by Author "Balleri, Alessio"

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Open Access
3D conformal antennas for radar applications
(2018) Fourtinon, L; Balleri, Alessio
Embedded below the radome of a missile, existing RF-seekers use a mechanical rotating antenna to steer the radiating beam in the direction of a target. Latest research is looking at replacing the mechanical antenna components of the RF seeker with a novel 3D conformal antenna array that can steer the beam electronically. 3D antennas may oer signicant advantages, such as faster beamsteering and better coverage but, at the same time, introduce new challenges resulting from a much more complex radiation pattern than that of 2D antennas. Thanks to the mechanical system removal, the new RF-seeker has a wider available space for the design of a new 3D conformal antenna. To take best benets of this space, dierent array shapes are studied, hence the impact of the position, orientation and conformation of the elements is assessed on the antenna performance in terms of directivity, ellipticity and polarisation. To facilitate this study of 3D conformal arrays, a Matlab program has been developed to compute the polarisation pattern of a given array in all directions. One of the task of the RF-seeker consists in estimating the position of a given target to correct the missile trajectory accordingly. Thus, the impact of the array shape on the error between the measured direction of arrival of the target echo and its true value is addressed. The Cramer-Rao lower bound is used to evaluate the theoretical minimum error. The model assumes that each element receives independently and allows therefore to analyse the potential of active 3D conformal arrays. Finally, the phase monopulse estimator is studied for 3D conformal arrays whose quadrants do not have the same characteristics. A new estimator more adapted to non-identical quadrants is also proposed.
Open Access
Advanced cognitive networked radar surveillance
(IEEE, 2021-06-18) Jahangir, Mohammed; Baker, Chris J.; Antoniou, Michail; Griffin, Benjamin; Balleri, Alessio; Money, David; Harman, Stephen
The concept of a traditional monostatic radar with co-located transmit and receive antennas naturally imposes performance limits that can adversely impact applications. Using a multiplicity of transmit and receive antennas and exploiting spatial diversity provides additional degrees of design freedom that can help overcome such limitations. Further, when coupled with cognitive signal processing, such advanced systems offer significant improvement in performance over their monostatic counterparts. This will also likely lead to new applications for radar sensing. In this paper we explore the fundamentals of multistatic network radar highlighting both potential and constraints whilst identifying future research needs and applications. Initial experimental results are presented for a 2-node networked staring radar.
Open Access
Ambiguity function and accuracy of the hyperbolic chirp: comparison with the linear chirp
(2016-07-06) Balleri, Alessio; Farina, Alfonso
In this paper, we derive the Ambiguity Function (AF) of a narrowband and a wideband hyperbolic chirp. We calculate the second derivatives of the squared amplitude of the narrowband Complex Ambiguity Function (CAF) and use them to calculate the Fisher Information Matrix (FIM) of the estimators of the target range and velocity. The FIM is then used to calculate the Cramer-Rao Lower Bounds (CRLB) of the variance of the estimators and to ´ carry out an analysis of estimation performance and a comparison with the case of a liner chirp with a rectangular and a Gaussian amplitude modulation. The analysis and the calculations of the CRLB are also extended to a train of hyperbolic chirps. Results corroborate that at narrowband the hyperbolic chirp is less Doppler tolerant than the linear chirp and show that the hyperbolic chirp provides a comparable measurement accuracy to the linear chirp. Results at wideband corroborate the superior Doppler tolerance of the hyperbolic chirp with respect to that of the linear chirp.
Open Access
Baseband version of the bat-inspired spectrogram correlation and transformation receiver
(Institute of Electrical and Electronics Engineers, 2016-06-01) Georgiev, Krasin; Balleri, Alessio; Stove, Andy; Holderied, M.
Echolocating bats have evolved an excellent ability to detect and discriminate targets in highly challenging environments. They have had more than 50 million years of evolution to optimise their echolocation system with respect to their surrounding environment. Behavioural experiments have shown their exceptional ability to detect and classify targets even in highly cluttered surroundings. The way bats process signals is not exactly the same as in radar and hence it can be useful to investigate the differences. The Spectrogram Correlation And Transformation receiver (SCAT) is an existing model of the bat auditory system that takes into account the physiology and underlying neural organisation in bats which emit chirped signals. In this paper, we propose a baseband receiver equivalent to the SCAT. This will allow biologically inspired signal processing to be applied to radar baseband signals. It will also enable further theoretical analysis of the key concepts, advantages and limitations of the "bat signal processing" for the purpose of target detection, localisation and resolution. The equivalence is demonstrated by comparing the output of the original SCAT to that of our proposed baseband version using both simulated and experimental target echoes. Results show that the baseband receiver provides compatible frequency interference pattern for two closely located scatterers.
Open Access
Bio-inspired processing of radar target echoes
(2018-07-20) Georgiev, Krasin; Balleri, Alessio; Stove, Andy; Holderied, Marc W.
Echolocating bats have evolved the ability to detect, resolve and discriminate targets in highly challenging environments using biological sonar. The way bats process signals in the receiving auditory system is not the same as that of radar and sonar and hence investigating differences and similarities might provide useful lessons to improve synthetic sensors. The Spectrogram Correlation And Transformation (SCAT) receiver is an existing model of the bat auditory system that takes into account the physiology and the neural organisation of bats that emit broadband signals. In this study, the authors present a baseband receiver equivalent to the SCAT that allows an analysis of target echoes at baseband. The baseband SCAT (BSCT) is used to investigate the output of the bat-auditory model for two closely spaced scatterers and to carry out an analysis of range resolution performance and a comparison with the conventional matched filter. Results firstly show that the BSCT provides improved resolution performance. It is then demonstrated that the output of the BSCT can be obtained with an equivalent matched-filter based receiver. The results are verified with a set of laboratory experiments at radio frequencies in a high signal-to-noise ratio.
Open Access
Bio-inspired two target resolution at radio frequencies
(IEEE, 2017-06-06) Georgiev, Krasin; Balleri, Alessio; Stove, Andy; Holderied, Marc
Echolocating bats show a unique ability to detect, resolve and discriminate targets. The Spectrogram Correlation and Transformation (SCAT) receiver is a model of the Eptesicus fuscus auditory system that presents key signal processing differences compared to radar which may offer useful lessons for improvement. A baseband version of the SCAT is used to investigate advantages and disadvantages of bat-like signal processing against the task of target resolution. The baseband receiver is applied to RF experimental data and results show higher range resolution than the reciprocal of the transmitted bandwidth can be achieved for two closely spaced scatterers.
Open Access
Biologically inspired processing of radar and sonar target echoes
(2017-10-31) Georgiev, Krasin; Balleri, Alessio
Modern radar and sonar systems rely on active sensing to accomplish a variety of tasks, including detection and classification of targets, accurate localization and tracking, autonomous navigation and collision avoidance. Bats have relied on active sensing for over 50 million years and their echolocation system provides remarkable perceptual and navigational performance that are of envy to synthetic systems. The aim of this study is to investigate the mechanisms bats use to process echo acoustic signals and investigate if there are lessons that can be learned and ultimately applied to radar systems. The basic principles of the bat auditory system processing are studied and applied to radio frequencies. A baseband derivative of the Spectrogram Correlation and Transformation (SCAT) model of the bat auditory system, called Baseband SCAT (BSCT), has been developed. The BSCT receiver is designed for processing radio-frequency signals and to allow an analytical treatment of the expected performance. Simulations and experiments have been carried out to confirm that the outputs of interest of both models are “equivalent”. The response of the BSCT to two closely spaced targets is studied and it is shown that the problem of measuring the relative distance between two targets is converted to a problem of measuring the range to a single target. Nearly double improvement in the resolution between two close scatterers is achieved with respect to the matched filter. The robustness of the algorithm has been demonstrated through laboratory measurements using ultrasound and radio frequencies (RF). Pairs of spheres, flat plates and vertical rods were used as targets to represent two main reflectors.
Open Access
Biomimetic echolocation with application to radar and sonar sensing
(IEEE Institute of Electrical and Electronics, 2014-03-25T00:00:00Z) Baker, C. J.; Smith, Graeme E.; Balleri, Alessio; Holderied, M.; Griffiths, H. D.
Nature provides a number of examples where acoustic echolocation is the primary sensing modality, the most well-known of these being the bat, whale and dolphin. All demonstrate a remarkable ability to "see with sound". Using echolocation they navigate, locate and capture prey. As species, they have not only survived but have thrived in all their individual environments, often solely reliant on echolocation. All of these creatures are inherently cognitive. They all maintain a perception of their environment through the nervous system that allows them to take actions. In this paper we focus on the bat as an example of a cognitive system exploiting a memory-driven perception-action cycle, enabling it to navigate and interact with its environment. The key conceptual components of cognition and how it could be applied to man-made echoic sensors is introduced. This is followed by a description of how echoic flow fields, a bio-inspired technique that bats have been shown to use, fit guidance and control problems. We then go on to explain how bats are able to reliably distinguish between different targets. A combination of the theory and examples is used to demonstrate the vast potential for advancing the capability of made in man-made systems by adopting aspects of natural echolocating cognitive dynamic systems.
Open Access
Bistatic radar signature of buried landmines
(IET, 2017-10) Lombardi, F.; Griffiths, H. D.; Balleri, Alessio
With the proliferation of low-intensity conflict, landmines have proven to be one of the weapons of choice for both government and guerrilla forces around the world. Recent improvements to mine technology pose increasingly significant problems for demining operations, requiring the constant upgrading of countermine technologies. Ground Penetrating Radar (GPR) is one of the most exhaustively researched topics in the detection of buried mines as it can be used to detect non-metallic and plastic mines. However, identification and recognition are still unsolved problems, due to the scattering similarity between mines and clutter objects. This study provides an experimental evaluation of the improvements that a bistatic approach could yield and what can be gained from investigating the angular dependencies of the landmine radar signature.
Open Access
Characterisation of sidelobes for multibeam radar based on quasi-orthogonal LFM waveforms
(IEEE, 2020-06-11) Balleri, Alessio; Kocjancic, Leon; Merlet, Thomas
Multibeam radars (MBRs) enable multiple independent channels by simultaneously exploiting spatial and waveform diversity. Orthogonal waveforms are employed to form multiple independent antenna beams, each one providing a different function and using different dedicated radar resources. This paper investigates sidelobe levels in MBRs and presents a comparison with those of an Electronic Steerable Array (ESA) that employs a single waveform in transmission to generate multiple simultaneous beams. Simulations are carried out for a 3-channel MBR transmitting quasi-orthogonal Linear Frequency Modulated (LFM) waveforms at Ku band. The response of the MBR to an ideal point target as a function of aspect angle as well as that to multiple targets in different locations has been investigated. Results corroborate the analytical findings and show that the sidelobe levels with respect to angle, at the target range, are attenuated by the cross-ambiguity function properties between the waveforms employed. The range response to a target in low channel isolation suffers from cross-channel interference that may alter the noise floor characteristics of the radar, hence stressing the importance of suitable waveform selection.
Open Access
Characterization of the internal structure of landmines using ground penetrating radar
(IEEE, 2020-02-13) Lombardi, Federico; Griffiths, Hugh D.; Lualdi, Maurizio; Balleri, Alessio
One of the principal limitations of employing Ground Penetrating Radar (GPR) for landmine detection is the presence of clutter, i.e. reflections from the surrounding environment which might interfere with the landmine echoes. Clutter presents similar scattering characteristics of typical targets and may significantly raise the detection threshold of the system. A capability to characterise the internal structure of a buried target might provide key unique information to develop advanced landmine-clutter discrimination algorithms, considering that the presence of internal scattering components can be univocally associated to man-made targets. In this paper, the possibility of identifying and characterising these contributions from the GPR signature of a landmine is numerically assessed and experimentally validated. The simulated response from a landmine-like target shows that the presence of the internal structure generates additional reflection peaks, as a consequence of the layered structure of the object, and the field trials corroborate that it is possible to identify these scattering components and delineate their spatial distribution.
Open Access
Coordination of optimal guidance law and adaptive radiated waveform for interception and rendezvous problems
(Institution of Engineering and Technology, 2017-02-22) Balleri, Alessio; Farina, Alfonso; Benavoli, Alessio
The authors present an algorithm that allows an interceptor aircraft equipped with an airborne radar to meet another air target (the intercepted) by developing a guidance law and automatically adapting and optimising the transmitted waveform on a pulse-to-pulse basis. The algorithm uses a Kalman filter to predict the relative position and speed of the interceptor with respect to the target. The transmitted waveform is automatically selected based on its ambiguity function and accuracy properties along the approaching path. For each pulse, the interceptor predicts its position and velocity with respect to the target, takes a measurement of range and radial velocity and, with the Kalman filter, refines the relative range and range rate estimates. These are fed into a linear quadratic Gaussian controller that ensures the interceptor reaches the target automatically and successfully with minimum error and with the minimum guidance energy consumption.
Open Access
Deception jamming against anti-ship missiles which use doppler beam sharpening modes
(2020-02) Frazer, Gareth; Balleri, Alessio; ;
Missile seekers are becoming increasingly more capable of using Doppler Beam Sharpening (DBS) modes as part of the homing cycle, which requires new countermeasures against this mode. One type of countermeasure, is to create false targets within the seeker DBS image. This thesis presents two implementation methods to insert false targets into DBS images. Both methods are used to create false targets at a precise location within a seeker DBS image, but are implemented in different ways. The first method proposes repeat jamming with a time-varying delay, whilst the second proposes a fixed delay and adding a specific Doppler shift to received waveforms. The effects of tracking errors on the position of the false target are analysed, both analytically and with simulations and used to assess the practical implementation of the jamming scheme. An experimental DBS system was built to test the effectiveness of the jamming scheme against a platform moving in steps and assess errors caused by incorrectly estimating the seeker trajectory. The overall result of the thesis is that using the derived jamming methods, false targets can be created at specific locations in the DBS image of the victim radar, providing the trajectory of the victim radar is known.
Open Access
Deception jamming against doppler beam sharpening radars
(IEEE, 2019-09-16) Frazer, Gareth; Balleri, Alessio; Jacob, George S.
Missile seekers are becoming increasingly more capable of using Doppler Beam Sharpening (DBS) modes as part of the homing cycle. This paper develops jamming theory and uses it for practical implementation of inserting false targets into a DBS image. The theory is also developed for how incorrect estimations of the seeker trajectory can affect the quality and location of the false target. The simulated and experimental results show how received missile seeker waveforms can be modified to create false targets at desired locations.
Open Access
Deception jamming against doppler beam sharpening radars
(IEEE, 2020-02-11) Frazer, Gareth; Balleri, Alessio; Jacob, George
Missile seekers are becoming increasingly more capable of using Doppler Beam Sharpening (DBS) modes as part of the homing cycle, which requires new countermeasures against this mode. One type of countermeasure, is to create false targets within the seeker DBS image. This paper proposes a jamming technique to generate false targets at a precise location within a seeker DBS image, by both delaying and adding a Doppler shift to received waveforms. The effects of tracking errors on the position of the false target are analysed, both analytically and with simulations and used to assess the practical implementation of the jamming scheme. An experimental DBS system was built to test the effectiveness of the jamming scheme against a platform moving in steps and assess errors caused by incorrectly estimating the seeker trajectory.
Open Access
Dependence of landmine radar signature on aspect angle
(IET, 2017-02-06) Lombardi, F.; Griffiths, H. D.; Wright, L.; Balleri, Alessio
Antipersonnel landmines have been indiscriminately used since World War II, and their longterm persistence in the ground creates a barrier to development in a large number of countries, forcing people to live in constant fear. Therefore, there is a growing demand for reliable landmine inspection systems that could achieve an exhaustive detection to and return the land to its normal use. Due to its ability of detecting both metallic and non-metallic objects, Ground Penetrating Radar (GPR) has successfully been demonstrated to be a meaningful method for detecting landmines, allowing faster and safer operations. Most landmines may be considered as multiple layered dielectric cylinders, which each interface causes a reflection, properties that are hardly expected in other commonly encountered clutter objects. Considering that these features have their own angular pattern and will respond differently to different illumination, landmines are expected to produce signatures that present some discriminant features that could be used for reducing the false alarm rate of GPR equipment. In this paper, a set of measurements of three inert landmines has been acquired to study and characterise landmine signatures as a function of the antenna orientation relative to the landmine and target aspect angle.
Open Access
Design and development of K-Band FMCW radar for nano-drone detection
(IEEE, 2020-12-04) Zulkifli, Safiah; Balleri, Alessio
Nano-drones, are insect-like size drones with a capability of intrusion to provide intelligence and potentially violate secure establishments and public privacy rights. Nano-drones are already an existing technology which is becoming more and more available, portable, affordable and easily operated. As such, they may soon become a plausible defence and security threat. This paper presents the design and development of a K-Band FMCW radar prototype for nano-drone detection. The FMCW radar prototype consists of connectorised components operating at a carrier frequency of 24 GHz and offer high parameter selection flexibility. Experiments have been carried out in order to evaluate the system performance. Results show that a small Arcade PICO Drone Nano Quadcopter (smaller than 5 cm) could be detected, and that its micro-Doppler signature could be extracted from data.
Open Access
Design of a stacked circularly polarized slot-patch antenna for X-band applications
(IEEE, 2024-07-19) Pascarella, Francesca; Mugnaini, Sara; Balleri, Alessio; Scarselli, Chiara; Brizi, Danilo; Monorchio, Agostino
This paper introduces a numerically investigation of a compact stacked Circularly Polarized (CP) slot-patch antenna designed to operate in X-band (8 -12 GHz). The proposed solution features a coaxially fed circular radiating patch etched on a dielectric substrate, which includes two sector notches positioned on opposite sides at a 45° inclination to achieve circular polarization. Two additional dielectric substrates are placed on the top of the radiating patch, with a parasitic passive patch positioned on each, with the aim of enlarging the overall operating bandwidth. The numerical results demonstrated that the configuration is able to cover a 2.2 GHz band, achieving a minimal Axial Ratio (AR) of 1.2 dB and a gain of 7.4 dB at 10 GHz.
Open Access
Development of a K-band FMCW flexible radar prototype for detection and classification of nano-drones
(2020-12) Zulkifli, Safiah Binti; Balleri, Alessio
Nano-drones of the size of an insect can be used to perform stealthy surveillance or to gather intelligence crucial to attack roles at a relatively short range and within enclosed spaces and buildings. Conventional radar systems have been optimised to detect and classify bigger targets and are not specifically designed to detect nano-targets of less than 5 cm in size. Hence, this project aims to develop a radar system to detect and classify an insect-like size drone that corresponds to a low RCS. This will exhibit challenges due to the nature of the weak echoed signal that will be masked by an uninterested target with a stronger echoed signal. To tackle this sort of problem, micro Doppler extraction is applied for better target detection. This type of target that consists of a bladed propeller will give rise to a significant micro-Doppler signature that will contribute to the discernment of the interested target. An ad-hoc S-band FMCW radar prototype using off-the-shelf components An ad-hoc S-band FMCW radar prototype using off-the-shelf components has been successfully delivered. This prototype act as a groundwork for the next research phase of design and development for a higher frequency. Then, with the strong foundation of the S-band demonstrator, a flexible K-band FMCW radar prototype has successfully delivered aiming to meet the research purpose. The radar prototype offers a wide range of flexibility for the user to select the radar parameters (like operating frequency, ramp duration, bandwidth and integration time) and configure its performance. It will collect the signatures of real targets (nano-drone model) so that their performance can be assessed on experimental data. The results demonstrated that a nano-drone, a small size of less than 5 cm can be detected with the radar prototype developed.
Open Access
Development of a passive dual channel receiver at L-band for the detection of drones
(IEEE, 2022-06-02) Griffin, Benjamin; Balleri, Alessio; Baker, Chris; Jahangir, Mohammed; Harman, Stephen
Staring radars use a transmitting static wide-beam antenna and a directive digital array to form multiple simultaneous beams on receive. Because beams are fixed, the radar can employ long integration times to detect slow low-RCS targets, such as drones, which present a challenge to traditional air surveillance radar. The use of multiple spatially separated receivers cooperating with the staring transmitters in a multistatic network allows multi-perspective target acquisitions that can help mitigate interference and ultimately enhance the detection of drones and reduce estimation errors. Here, the development and experimental results of a passive, dual-channel, L-band receiver are presented. The receiver has been used to take measurements of both moving vehicles of drones in flight using a bistatic staring transmitter. An analysis of the receiver is presented using GPS is used to quantify the estimation performance of the receiver.